The invention pertains to a rotary sensor arrangement for elements that can be turned relative to surrounding elements, in particular for shafts.
In gear shafts, steering valve shafts, power steering systems and the like, it is necessary to determine the steering angle and, if so required, the steering angle velocity. In modern electrohydraulic steering systems, this information serves for adapting the flow rate of the pump to the given current steering velocity.
Since the available space for auxiliary assemblies, e.g., gears, steering valves and the like, is limited in the manufacture of modern automobiles, for which the present invention is particularly intended, it is necessary to integrate the rotary sensor arrangements into the given assembly. This is also desirable for reasons of minimal manufacturing costs, low assembly expenditures and the like.
Known sensor arrangements usually contain assemblies that can be turned relative to one another. However, these assemblies also form a unit relative to one another, i.e., sensor modules. The main reason for this can be seen in the fact that the assemblies must be arranged relative to one another in a predetermined relation, i.e., with respect to location, direction, spacing and the like. Otherwise, a flawless sensor function with a sufficient accuracy cannot be ensured. One example for such an arrangement are Hall sensor systems, in which a magnetic pulse ring is surrounded by a Hall sensor ring. These rings must maintain a fixed, predetermined distance from one another. Consequently, these rings are preassembled relative to one another and form a sensor module, usually a ball bearing that, for example, is mounted on a shaft. The outer ring is secured from rotating and is electrically connected. One disadvantage of this known sensor module is that the entire shaft assembly must be removed if malfunctions occur, subsequent adjustments must be made, etc., because the sensor would otherwise not be accessible. This removal is particularly undesirable with power steering systems because the entire steering valve and, in certain instances, even the complete steering system must be removed. When using sensor modules with two concentric elements of the previously described type which, for example, are also used in optoelectronic rotary measuring methods, the requirements regarding interchangeability or ease of assembly cannot be fulfilled.
Starting from the state of the art, the present invention is based on the objective of disclosing a rotary sensor arrangement in which the sensor is accessible without having to remove any assemblies, wherein said sensor arrangement also allows an economical integration into existing assemblies.
According to the invention, this objective is attained with a rotary sensor arrangement for elements that can be turned relative to surrounding elements, in particular, for shafts, which consists of at least two sensor units that can be mounted separately from one another, wherein one sensor unit is arranged on the rotatable element and at least one second sensor unit is arranged on an element that is stationary relative to the rotatable element, and wherein at least the second sensor unit can be accessed and removed independently of the state of installation of the rotatable element.
According to the invention, completely different sensor units can be mounted in completely different fashion. In this case, it is essential that at least one sensor unit can be mounted on a relatively stationary element, e.g., a housing, and independently of the state of installation of, for example, a shaft. Consequently, the element is accessible at all times and can be removed independently of the state of installation of the shaft.
The element to be arranged on the rotatable element, e.g., a shaft, may, for example, be realized annularly. This element may, for example, consist of a magnetic pulse ring that is mounted on the input shaft of a steering valve. When carrying out an optoelectronic measurement of the angle of rotation, this element consists of a ring provided with corresponding optical markings. This ring may be mounted at a suitable location on the input shaft so that it surrounds said input shaft. According to one advantageous proposal of the invention, at least the second sensor element is realized analogously to a ring segment, i.e., this sensor element may be arranged on the housing side opposite to the rotatable sensor unit. The ring segment may, for example, contain Hall sensors, optoelectronic sensors or the like.
According to one particularly advantageous proposal of the invention, the sensor units are realized in such a way that they slide on one another. This can be realized in particularly advantageous fashion by arranging a plastic layer on one or both units. A fixed, predetermined distance of the units relative to one another is ensured by the plastic layer formed between the surfaces of the sensor units which face one another, i.e., a highly accurate sensor for shafts that run untrue or for unfavorable deviations of dimensional tolerances is realized. In addition, this measure makes it possible for the sensor units to slide on one another in nearly frictionless fashion.
The sensor unit that is essentially realized in the form of a rod or a ring segment may be mounted on the steering shaft of the steering valve similar to a thrust piece, namely on the housing side at the elevation of the magnetic pulse ring. This sensor unit may be realized in the form of a plastic thrust piece and guided axially and tangentially in the housing. According to one advantageous proposal of the invention, the sensors as well as the evaluation circuit, line connections, plugs and the like are cast into the plastic material. The thrust piece may be mounted and fixed in a housing bore in spring-loaded fashion, preferably by means of a screwed-on cover, a clipped-on cover or a similar arrangement, wherein a helical spring is preferably arranged in between. The sensor may be connected to a thrust piece by means of parallel, essentially linear spring elements. Consequently, the spring elements fulfill the guide function and realize the electrical connection. Alternatively, a cover with membrane function, i.e., an elastic cover, may be used. Due to these measures, the thrust piece is guided and spring-mounted, wherein the housing is simultaneously sealed by the cover.
According to one particularly advantageous proposal of the invention, the rotary sensor arrangement according to the invention is arranged in a steering gear, in particular, on the steering valve. In this case, the input shaft of the steering valve is provided with a magnetic pulse ring, and the Hall sensors are cast into a plastic thrust piece that is arranged in a bore in the steering gear housing.
Consequently, the invention also discloses a completely new type of steering valve or steering gear, wherein said steering valve or steering gear contains a steering sensor arrangement for determining the steering angle, the steering angle velocity and the like. This steering sensor arrangement is formed by a pulse transmitter attached onto the input shaft and a sensor arrangement arranged on the side of the gear housing. The steering gear according to the invention preferably contains a Hall sensor arrangement that is mounted in the housing opposite to the magnetic pulse ring that is attached onto the input shaft. The Hall sensor arrangement preferably consists of a plastic thrust piece, into which the Hall sensors, the evaluation circuit, the connecting lines and the like are cast. The plastic thrust piece is prestressed by a spring that is subjected to tension by a screwed-on cover, a clipped-on cover or the like.
The invention allows compensation of tolerances. For this purpose, a very wide pulse ring that is arranged opposite to a narrow Hall sensor thrust piece may, for example, be used. The Hall sensor thrust piece may also contain an axial limit stop for the pulse ring. One of the sensor units may be realized integrally with the shaft or the housing. The pulse ring, in particular, may be realized integrally with the shaft or be directly integrated into this shaft. This applies analogously to the thrust piece and the housing.